Gas blast circuit breaker



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Reiuued Apr. 6, 1943 GAS BLAST CIRCUIT BREAKER Bryce W. Wyman, Yeadon, Pa., assignor to General Electric Company, a corporation of New York ' Original No. 2,306,240, dated December 22, 1942, Serial No. 398,128, June 14, 1941. Application for reissue February 4, 1943, Serial No. 474,727

40mins. (01. 200-148) My invention relates to gas blast circuit breakers wherein the arc to be interrupted is confined in an insulating structure and traversed by a blast of gas flowing at high velocity under pressure, and has for its principal object the provision of an improved method of operation of and structural arrangement for a circuit breaker of the aforesaid type so that it is particularly adapted for interrupting heavy currents throughout awide range of line voltage.

The interruption of heavy overload and short .circuit currents at moderate voltages, suchas 15 km, has been efiiciently accomplished by a cross-blast type air circuit breaker wherein the arc isdriven by a transverse blast of gas into an 'arc'chute having insulating barriers or bartitions extending edgewiseto and transversely of the arc stream. The hot blast gases flowin from the region of arcing are directed to exhaust through the chute passages defined by the aforesaid partitions; Such a circuit breaker is in which are'mounted for relative movement the breaker contacts 2 and 3. The contact 2, which disclosed and claimed in application Serial No.

303,126 filed November 6, 1939, by D. C. Prince et al. for Circuit breaking apparatus and method of operating the same now Patent No. 2,284,842 issued June 2, 1942 and assigned to the same assignee as the present invention. When this type circuit breaker is used for interrupting power currents at appreciably higher voltages, such as 50 kv., insulation difliculties appear and, instead of clearing the circuit, the breaker may fail due tofiashover.

In accordance with my invention, the desirable current interrupting characteristics of'the aforesaid cross-blast type breaker are retained and the volta e range of the breaker is appreciably increased by incorporating in th circuit breaker structure auxiliary means for subjecting the arc to a high velocity axial blast prior to completion of the breaker opening operation.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view in section of a gas blast circuit breaker embodying my invention in an initial stage.

of the opening operation, and Fi 2 is a similar view illustrating the final stage of a high voltage circuit interrupting operation.

The circuit breaker illustrated by way of example in Figs. 1 and 2 comprises an insulating housing I defining arc extinguishing structure may be o1 any suitable type, such as the resilient finger type, is shown as fixed in the housing and is connected to one line terminal of the breaker indicated at 2'. The contact 3 is formed as a blade member and is reciprocally movable in the insulating housing with respect to the fixed contact 2, and is electrically connected as indicated to the other line terminal of the breaker at 3'.

The contacts 2 and 3 are separable within a narrow slot-like passage 4 in the housing and this passage is arranged to be connected at one side to a source of gas pressure indicated at 5, and at the opposite side (for the first part of the contact opening movement) with an arc chute 6. The chute 6 is provided with at least one insulating barrier or partition 1 dividing the chute into blast passages that are vented to atmosphere at 8. The hot blast gases flowing from the region of arcing at 4 arecooled by means of spaced metallic plates disposed edgewise to the gas flow as indicated at 5. The insulating barrier l is preferably composed of a vaporizable insulating material, such as hard fibre, that does not lose its dielectric strength in the presence of the are. An arc chute of this character is disclosed and claimed in the Prince et al. application above-identified.

When the breaker is to be opened, the movable contact 3 is actuated by suitable means (not shown) toward the left as viewed in Fig. 1 so as to separate from contact 2 and form an arc gap opposite the entrance of the chute 6. practically the same instant, the interrupting gas is admitted under pressure by way of the conduit 5 to the passage 4 so that the resulting blast of gas necessarily traverses the are between the contacts 2 and 3 and drives it sideward against the insulating barrier l on its way to exhaust from the chute passage 8. At this stage of the opening operation, the gas blast is eflective to interrupt very heavy currents at the first current zero.

In the case of high voltage circuits and Cll cuits having a high rate of rise of recovery voltage, this interruption at the first current zero may not be permanent and the dielectric strength of the gap so formed between the contacts may be insufficient to prevent voltage breakdown and reestablishment of arcing. ,This difiiculty in clearing the circuit is overcome in accordance with my invention by connecting in shunt with the contacts during the initial opening opera- Atv tion, and in series therewith for the final interrupting operation an auxiliary gas blast circuit breaker of the axial blast type, preferably in series with a resistance.

ing the initial part of the opening movement to shunt the original arc gap and is placed in series with the blade contact and breaker terminals immediately upon interruption of the are at the first current zero in the chute 8. In a simplified arrangement, the auxiliary breaker ll comprises a movable rod contact II that is resiliently biased, such as bya spring I2, into sliding electrical contact at H with the blade I. The rod contact II is also electrically connected through a flexible conductor ii to a terminal indicated at II, which is in turn electrically connected through a resistance I! to the breaker line terminal! as indicated at IS. The rod contact H is guided for reciprocal movement in a cylinder l1 formed in the main insulating housing and includes a piston l8 which functions both as a guide for the rod contact and as a valve for uncovering the blast vent port l9 leading from the cylinder H. The rod contact II is operable within a restricted nozzle-like passage Ill communicating with the cylinder. I! located a short distance beneath the point of contact engagement with the blade I.

From the above description, it will be seen that the current zero through this connection will be 01 decreased magnitude, and in addition the power 'factor will be improved. Therefore, when the blade contact 3 in continuing its opening movement uncovers the aforesaid nozzle passage and moves out of engagement with the rod contact ll of the auxiliary breaker, the resulting are,

which is immediately drawn into the restricted nozzle 20 due to the action of blast pressure from on the piston l8,'is more'readily extinguished by the high velocity constricted axial blast within the insulating nozzle as clearly indicated by Fig. 2. When the auxiliary breaker contact reaches the position shown by Fig. 2', the blast passage I! is also uncovered so that the gas blast can sweep unhindered through and longitudinally of the arc path. This blast flows through as well as longitudinally (or axially) of the arc stream and the arrangement avoids many of ,the insulation difficulties of other-types of gas blast breakers. The axial blast arrangement above described has been found to be particularly adapted for interrupting high voltage circuits, although it is not so well adapted as the cross blast type above described for interrupting heavy currents. Therefore by first interrupting th heavy current arc momentarily at a. current zero, at which time a resistance is automatically inserted in the circuit, and then by interrupting the reduced current in the manner above described, it will be seen that I provide means for interrupting high voltage power circuits notheretofore provided in the known types of gas blast breakers. I

It will also be seen that the gas pressure within the nozzle passage is caused to build up until 15 the contact piston-valve It opens the blast exhaust vent. This increased gas pressure in the region of 'arcin is an additional asset during the interruption operation since the dielectric strength of the gas is thereby increased.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent oi the United States is:

l. A gas blast circuit breaker for high voltage power circuits comprising contacts including a movable contact separable to form an arc gap, an arc chute having an entrance opposite the initially formed part of said gap, means for directing an interrupting blast of gas through said initially formed part of the arc gap to drive the are into said chute for extinguishing it at a current zero, a resistance arranged to be connected in shunt with said part of said gap whereby a reestablished power current is reduced, and a separately operable auxiliary gas blast circuit -a-nuzzie-like arc interrupting passage for said last-formed arc gap, and means for directin a second gas blast into saidnozzle-like passage axially of the are for finally interrupting thereduced current are therein.

2. A gas blast circuit breaker for high voltage power circuits comprising relatively fixed and movable contacts separable to form an arc gap, an arc chute having an entrance opposite the initially formed part of said gap, means for directing an interrupting blast of gas through and across'said initially formed part of the arc gap to drive the are into said chute for extinguishing it at a current zero, a resistance arranged to be connected in shunt with said part of said gap whereby a reestablished power current is reduced,

and a separately operable auxiliary gas blast circuit breaker included in said shunt connection having a separate movable contact operable in response to gas pressure to form a second arc.

gap, said auxiliary breaker having a nozzle-like arc interrupting passage in which said second arc 'gap is formed, and means for directing a second gas blast into said nozzle-like passage axially oi the arc for fina1ly interrupting the reduced current are therein, said second gas blast also being effective to build uppressure in said passage to cause opening movement'oi said movable auxiliary breaker contacts.

3. A gas blast circuit breaker for high voltage power circuits'comprising relatively movable contact structure separable to form an arc gap, an arc chute havingdnsulating partitions forming arc barriers and having an entrance opposite an initially formed part of said gap, means for directing an interrupting blast of gas transversely through said initially formed part or the arc gap tively movable contact structure so as to form a second arc gap only after predetermined separation of said contact structure, said auxiliary breaker having a nozzle-like arc interrupting passage through which said auxiliary contact is movable and in which said second arc gap is formed, and means for directing a. second gas blast into and through said nozzle-like passage axially of the are causing opening movement of said auxiliary contact and for finally interrupting the reduced current arc.

4. A gas blast circuit breaker for high voltage power circuits comprising an arc chamber, sep arable contacts including a movable contact arranged to form an arc gap in said chamber, means for directing a blast of interrupting gas under pressure into said chamber and through said are gap for extinguishing the are at a current zero."

a resistance arranged to be connected in shunt with saidgap whereby a re-established power current is reduced in magnitude, and a separately operable auxiliary gas blast circuit'breaker included in said shunt connection having a separate movable contact'arranged to form a second arc gap, said auxiliary breaker having a nozzlelike are interrupting passage in which said second arc gap is formed, and means for directing a second gas blast into said nozzle-like passage axially of the are for finally interrupting'the reduced current are therein, said second gas blast also being effective to build up pressure in said" passage to cause opening movement of said movable auxiliary breaker contact.

BRYCE W. WYMAN. 

